Chippers are used to reduce branches, trees, brush, and other bulk wood products into small chips. A chipper typically includes an infeed chute, a feed system for controlling the feed rate of wood products into the chipper, a chipping mechanism, a drive system for powering the feed system and the chipping mechanism, and a discharge chute. For a description of an infeed chute see WOOD CHIPPER INFEED CHUTE, incorporated in its entirety herein by reference.
The chipping mechanism is commonly a large cutter drum that includes blades thereon. The drum is commonly driven by an engine via a belt. For a description of a belt drive system see BELT TENSIONING APPARATUS, incorporated in its entirety herein by reference. The drum is used to grind, flail, cut, or otherwise reduce the material fed into the chipper into small chips. Besides acting as the chipping mechanism, the drum is also commonly used to generate the air flow necessary to propel the cut chips out of the chipper.
In some prior art systems, paddles are attached to the ends of the drums to generate pressure needed to blow the chips out the discharge chute. FIG. 1 depicts a known chipper drum 10 within a drum housing 12. The chipper drum 10 is cylindrical in shape and includes a number of blades 14 and chip pockets 16 spaced apart on the cylindrical surface of the drum 10, and paddles 18 attached to the end surface of the drum 10. As the chipper drum 10 rotates about axis A in a counterclockwise direction B, it draws air into the inlet end 20 of the drum housing 12. The air flow between the chipper drum 10 and the housing 12 is accelerated by the paddles 18 through the outlet 22 of the chipper housing 12. This air flow blows the chips out of the chipper 10. In many prior art systems, the chips are blow out the rear of the chipper, which is undesirable as such chips are blow towards the operators who load the chippers from the rear.
FIG. 2 shows the chipper drum 10 rolled out flat into a rectangular shape. The paddles 18 in the known system extend beyond the edges of the cylindrical surface of the drum 10. The cylindrical surface or skin of the drum defines the cutting width W1 of the drum 10. The cutter drum housing width W3 needs to be large enough to allow space for the width W2 of the drum, which accounts for the portion of the paddles 18 that extend beyond the width W1 of the skin of the cutter drum 10.
Referring to FIG. 3, a schematic top view of a chipper 24 is shown. The chipper 24 includes a feed table 26 at the rear end of the chipper 24, a discharge chute 28 at the front end of the chipper 24, and a drum housing 12 therebetween. Feed rollers (not shown) are aligned with and positioned between the feed table 26 and the chipper housing 12. For a description of feed rollers see WOOD CHIPPER FEED ROLLER, incorporated in its entirety herein by reference. The engine 30 is positioned at the left side of the chipper 24, and the drive system 32 is positioned at a right side of the chipper 24. Increasing the width W3 of the chipper drum housing 12 would result in increasing the overall width WO of the chipper 24. Conversely, decreasing the width W3 of the chipper drum housing 12 would enable the overall width WO of the chipper to be decreased. Since it is desirable to minimize the overall width WO of the chipper 24 and maximize the effective cutting width W1 of the drum 10, it is desirable to minimize the difference between the width of the cutter drum housing W3 and the width W1 of the cutter drum surface.